Statistical Relaxation in Closed Quantum Systems and the Van Hove-Limit

We analyze the dynamics of occupation probabilities for a certain type of design models by the use of two different methods. On the one hand we present some numerical calculations for two concrete interactions which point out that the occurrence of statistical dynamics depends on the interaction structure. Furthermore we show an analytical derivation for an infinite system that yields statistical behaviour for the average over the whole ensemble of interactions in the Van Hove-limit.Comment: 11 pages, 8 figures, accepted for publication in European Physics Journal Special Topic

Necessity of eigenstate thermalization for equilibration towards unique expectation values when starting from generic initial states

We investigate dynamical equilibration of expectation values in closed quantum systems for realistic non-equilibrium initial states. Thereby we find that the corresponding long time expectation values depend on the initial expectation values if eigenstate thermalization is violated. An analytical expression for the deviation from the expected ensemble value is derived for small displacements from equilibrium. Additional numerics for magnetization and energy equilibration in an asymmetric anisotropic spin-1/2-ladder demonstrate that the analytical predictions persist beyond the limits of the theory. The results suggest eigenstate thermalization as physically necessary condition for initial state independent equilibration.Comment: 5 pages, 4 figure

Laparoscopic partial adrenalectomy for bilateral pheochromocytomas in a boy with von Hippel-Lindau disease

Objectives: In adults, increasing numbers of adrenalectomies for pheochromocytomas are performed laparoscopically. We report for the first time laparoscopic bilateral subtotal adrenalectomy for pheochromocytomas in an 8-year-old boy with von Hippel-Lindau disease. Methods, In July 1998, an 8-year-old boy with von Hippel-Lindau disease underwent laparoscopic adrenal-sparing surgery for bilateral pheochromocytomas. The boy presented with severe hypertension and two pheochromocytomas on both sides. Results: The child could be solely treated with laparoscopic adrenal-sparing surgery. The procedure was completed as planned. There were absolutely no intraoperative or postoperative complications. Postoperatively, catecholamine levels and hypertension went back to normal. At follow-up no residual tumor could be detected and no steroid replacement therapy was necessary. Conclusions: In experienced hands, laparoscopic adrenal-sparing surgery for pheochromocytomas is feasible and safe. Moreover, this minimal invasive approach represents an exceptional improvement in life quality, especially in children with von Hippel-Lindau disease since surgery will probably be necessary again and again in their future life. Copyright (C) 2000 S. Karger AG, Basel

Boltzmann-type approach to transport in weakly interacting one-dimensional fermionic systems

We investigate transport properties of one-dimensional fermionic tight binding models featuring nearest and next-nearest neighbor hopping, where the fermions are additionally subject to a weak short range mutual interaction. To this end we employ a pertinent approach which allows for a mapping of the underlying Schr\"odinger dynamics onto an adequate linear quantum Boltzmann equation. This approach is based on a suitable projection operator method. From this Boltzmann equation we are able to numerically obtain diffusion coefficients in the case of non-vanishing next-nearest neighbor hopping, i.e., the non-integrable case, whereas the diffusion coefficient diverges without next-nearest neighbor hopping. For the latter case we analytically investigate the decay behavior of the current with the result that arbitrarily small parts of the current relax arbitrarily slowly which suggests anomalous diffusive transport behavior within the scope of our approach.Comment: 6 pages, 4 figures, accepted for publication in Phys. Rev.

Effect of heat exposure on viability and contractility of cultured prostatic stromal cells

Objectives: Different thermotherapeutic modalities such as transurethral microwave therapy or transurethral needle ablation have been developed to provide effective alternatives to surgical management of benign prostate hyperplasia (BPH). The mechanisms of thermotherapy, however, are not completely understood. We developed a model to investigate the effects of heat application on stromal cell viability and contractility. Methods: Cells isolated from prostatectomy and cystoprostatectomy specimens were cultured in a selective medium. Temperatures ranging from 37 to 50 degrees C were applied for 1 h. Cell contraction was visualized by means of a cell culture microscope equipped with a time-lapse video system. For quantitative analysis, the percentage of contracting cells was evaluated; 10 mu M of phenylepherine were applied for adrenergic stimulation of the eel Is. Results: On immunohistochemistry and phase-contrast microscopy, these cells were identified as prostatic myofibroblasts. Incubation at 50 degrees C for 1 h in vitro induced immediate death of all cells, whereas at 45 degrees C a II cells survived. At 37 degrees C 55% of the cells were seen to contract after addition of phenylephrine. Immediately after incubation at 45 degrees C contraction rate decreased to 29%, but returned to 46% 1 day later. Conclusions: With this model, it is possible to study the mechanisms of thermotherapy in vitro. The results suggest that the effects of thermotherapy are due to the induction of cell death rather than to reduced stromal cell contractility. Furthermore, the data show that treatment is probably only successful if temperatures in excess of 50 degrees C are maintained. Copyright (C) 2000 S. Karger AG, Basel